What is it?

– Ebola, also called Ebola virus disease (EVD), is a very dangerous infection caused by a so-called filovirus. It was first discovered during an outbreak in 1976 in Zaire, now the Democratic Republic of the Congo, and named after a river near the place of the outbreak. Filoviruses get their name from the fact that they look like long, thin filaments when seen through a microscope.

– There are five known “species” of Ebola virus, each with their own characteristics: Ebola Zaire, Ebola Sudan, Ebola Reston, Ebola Tai Forest (also called Ivory Coast or Cote d’Ivoire) and Ebola Bundibugyo. The Marburg virus, a cousin of Ebola with largely the same symptoms, is a filovirus as well.

Seen under the microscope, the Ebola virus looks like a long thin thread. Credit: CDC

What are the symptoms?

– Ebola usually starts with non-specific complaints that could be mistaken for other diseases such as influenza or malaria. They include fever, fatigue, headaches, and muscle pain. There is often very severe diarrhea and vomiting as well. Some patients bleed from their nose or gums. (For the first three decades after it was discovered, Ebola was often called a viral hemorrhagic fever because of the severe bleeding seen in some patients. That term is not widely used anymore because many patients don’t bleed.)

– Up to 90% of patients have died in some outbreaks, but with good care, mortality can be much lower. During the big outbreak that struck West Africa between 2014 and 2016, there were 28,616 reported cases and 11,310 deaths, a mortality rate of just below 40%, according to WHO.

How does it spread?

– The Ebola virus lives primarily in animals. Researchers aren’t sure exactly which species are infected, but bats are a prime suspect. Sometimes, the virus will infect a human, probably when someone comes into contact with a bat or another infected animal. After that happens, the virus can start spreading between people and create a new outbreak. That does not always happen, however; sometimes, only one person becomes infected.

– Between people, the virus spreads primarily through contact with bodily fluids from patients. The most important ones are vomit, diarrhea, and blood, but semen and breast milk can be infectious as well. The bodies of deceased patients are very infectious.

– There have been more than 30 outbreaks since the 1970s, but until 2014, none had caused more than 500 cases. In other words, the West African outbreak was completely unprecedented in its size. Many factors played a role in that, including the poor health systems in the affected governments, a slow international response, a lack of trust in health workers, and the fact that the virus reached major cities.

The lifecycles of the Ebola virus. Credit: CDC

How is it treated?

– There are no specific drugs on the market against Ebola disease. Scientists have tested several candidate drugs during the big Ebola outbreak in West Africa in 2013 and 2014, but none of the studies gave a clear answer. For now, doctors use what is called “supportive care,” which means providing the best possible circumstances for the patient to recover.

– Because patients lose a lot of water, providing fluids is extremely important. When patients are too sick to drink, water can be given through an intravenous (IV) drip. But that requires a well-trained staff, which has often been in short supply in past outbreaks. As a result, many patients have not received an IV drip, which likely caused some to die from dehydration.

An Ebola treatment centre built by the United Kingdom in Kerry Town, Sierra Leone, in 2014 Credit: Carl Osmond/MOD

How can it be prevented?

– An Ebola vaccine isn’t commercially available yet. However, several vaccines are in development, and two were tested during the Ebola outbreak in West Africa. One, originally developed by scientists in Canada and now produced by Merck, had very promising results in Guinea. More tests are under way, and the vaccine has yet to be approved. But Merck has already produced 300,000 doses that could be used during the next outbreak. The vaccine was designed specifically to match the virus that occurred in West Africa. It’s not clear how well it works against other strains or species.

– In the absence of a vaccine, it’s extremely important to reduce the risk from infection for those who take care of Ebola patients. Family and friends should avoid all contact; health workers wear special suits, boots, and masks to protect themselves. Bodies of deceased Ebola patients pose a major risk and need to be buried safely. Traditional African burial practices, which sometimes include washing or touching the body, should be avoided. Because the Ebola virus can linger in male survivors for many months, the World Health Organization recommends that men practice safer sex for 12 months after their recovery or until their semen has twice tested negative for the virus.

– With all of these precautions, in addition to the isolation and monitoring of people who have come into contact with a patient, it’s possible to stop an Ebola outbreak in its tracks.

The Merck Ebola vaccine was shown to be effective during the West African outbreak of 2014. Credit: S. Hawkey/WHO


What’s the outlook?

– Ebola can never be eradicated, because the it’s impossible to get rid of the virus in animals. That means the virus will keep jumping into humans, and human outbreaks will continue to happen.

– The question will be how quickly future outbreaks are recognized, and how well they are contained. With good public health systems, effective governance and communication, and quick international action, it’s possible to nip epidemics in the bud and keep cases and deaths to a minimum.


The World Federation of Science Journalists has developed an online course for journalists, Covering Ebola.

The World Health Organization has a website about Ebola with extensive information about the West African epidemic.

A video explaining what Ebola does in the human body.

See how an Ebola treatment center run by Doctors Without Borders works.